Really Cool Stuff: Batteries That Last for Decades

Atomic energy provides an amazing source of concentrated power. The potential applications that have been proposed are widely varied. There is room for unlimited innovation and creativity.

Imagine what it would be like to have a battery that could provide power for several decades without recharging. Sounds almost like science fiction.

Fact, in this case, matches fiction.

The Voyager space probes carried devices called radioisotope thermal generators. (RTGs) These devices are simply amazing. They work on a simple principle. With semi conductor type materials, a current can be established by heating one side while cooling the other. The effect is known as the thermoelectric effect.

Nuclear Batteries

An RTG uses a radioactive material (like plutonium-238) as the heat source. This kind of plutonium spontaneously produces about one kilowatt of heat energy for every two kilograms of mass.

This energy level decreases slowly over time; after ten years the heat production is about 92 percent of the initial value. Even after 87 years, the material produces half as much heat as it did when it started.

The energy is actually released in the form of an alpha particle which can only travel a short distance before it stops. As the alpha particle slows, its motion is converted into heat. The battery material surrounding the plutonium provides adequate shielding. The batteries are so compact that a lightweight case can be built to withstand the stresses of atmosphere reentry without releasing any plutonium.

Nuclear batteries were essential to the success of the long distance space probes. Solar cells would not have provided enough power to operate the required equipment because the sun was too far away. Chemical batteries can provide enough power to run the instruments for a short period of time, but their total energy storage capacity is many times less than that of a nuclear battery.

The instruments and communications gear on the probes that provided such fantastic pictures of Satun and Jupiter would have been just dead weight without some form of power.

Better than the Rest

Nuclear batteries might have other uses. Imagine being able to buy a 10 year battery for a video camera, a laptop computer, or a portable telephone. Imagine how many rechargable NiCad batteries would have to be replaced during 10 years of continuous use.

Space program RTGs were too expensive for such use, but NASA’s first microprocessors were also far out of the reach of average human beings. By using the increasing stockpile of heat producing nuclear “waste” material, it is possible to dramatically reduce the cost of RTGs.